loc - get file location
Loc returns the current location within the file given by fn.
If fn is zero, the current file is used (see initio(io)).
For random files, the current location is measured in record lengths from the
beginning of the file; for other files, the location is measured in
IBMSECTORs (see io(inc)). Although the value returned is always a
whole number, this function returns a float to provide for large files.
This function implements the BASIC LOC function.
This function resets the current file.
Error 52 (Bad file number) is generated if fn does not refer
to an open user file.
Error 5 (Illegal function call) is generated if fn refers to a file
which is a pipe.
The Basmark QuickBASIC Programmerís Manual